Fabrication of complex crystals using kinetic control, chemical additives, and epitaxial growth

The growth kinetics of crystals of bis(imidazolium 2,6-dicarboxypyridine) M (II) dihydrate, where M = Cu, Ni, Co, Zn, and Mn, were studied in situ using atomic force microscopy. The aspect ratios of specific crystal facets were found to vary systematically with changes in the total concentration of the three components in this crystal system, which can be explained in terms of the growth kinetics at the (100) and (011) faces. Furthermore, inclusion of chemical additives in the growth solutions altered both the habit and faceting of these crystals. Crystallographic analysis of the molecular packing revealed a mechanism by which changes in the habit and faceting occur in the presence of chemical additives. This mechanism was exploited to facet selectively the (001) face for epitaxial studies between crystals containing different metal (II) ions. Epitaxial deposition of crystalline layers containing one metal (II) ion onto the (001) face of a crystal substrate containing a different metal (11) ion was found to be more difficult to achieve when compared to that for the (100) face. To overcome the difficulty of epitaxial growth on the (001) face of these crystals, crystalline gradients were employed, the results of which are demonstrated by the growth of complex crystals with distinct domains of crystal habit and molecular composition.